给定一个N*M的01矩阵，在可以交换列的情况下，求出最大的全1的子矩阵。

　　代码如下：

#include 
     
      #include 
      
       #include 
       
        #include 
        
         #define MAXN 1005using namespace std;int N, M, high[MAXN], temp[MAXN];char G[MAXN][MAXN];int deal(){    int Max = 0;    memcpy(temp, high, sizeof (high));    sort(temp+1, temp+M+1);    for (int i = M;  i >= 1; --i) {        if (temp[i]) {            Max = max((M-i+1)*temp[i], Max);        }    }    return Max;}int DP(){    int Max = 0;    for (int i = 1; i <= N; ++i) {        for (int j = 1; j <= M; ++j) {            if (G[i][j] == '1') {                 ++high[j];            }             else {                high[j] = 0;            }         }        Max = max(Max, deal());    }    return Max;}int main(){    while (scanf("%d %d", &N, &M) == 2) {        memset(high, 0, sizeof (high));        for (int i = 1; i <= N; ++i) {            scanf("%s", G[i]+1);        }        printf("%d\n", DP());    }     return 0;}